function Ajax(url:string,callback:any){
    //创建xhr
    const xhr = new XMLHttpRequest();

    //创建请求
    xhr.open('get',url);

    //发送请求

    xhr.send();

    //监听返回值
    xhr.onreadystatechange = () =>{
        //监听到健康的数据
        if(xhr.status === 200 && xhr.readyState === 4){
            callback(JSON.parse(xhr.response))
        }
    }
}